The Industrial Necessity of Leakage Current Verification Using Sm Doped Ceria Electrolytes in SOFCs and Future Applications

ABSTRACT

The use of Sm-doped Ceria electrolytes (SDC) in SOFCs (solid oxide fuel cells) lowers the open circuit voltage (OCV) below the Nernst voltage (Vth) obtained using Yttria-stabilized Zirconia (YSZ) electrolytes. The OCV is classically calculated with Wagner’s equation. However, using the SDC electrolytes requires both qualitative and quantitative experimental verification of leakage currents. Furthermore, there are limitations in Wagner’s equation, due to linear transport theory, when SDC electrolytes are used. The constant voltage loss without leakage current due to a mixed ionic and electronic conducting (MIEC) dense anode is proposed, and local equilibrium is considered to address the transition state during ion hopping. Only a carrier species having sufficient energy to overcome the activation energy can contribute to current conduction, which is described by a different constant in the definition of chemical potential and electrical potential. This difference explains results from the use of dense MIEC anodes. In this study, the industrial importance of this topic is discussed, and applications to future technologies are introduced.

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